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	Jan/Feb 2012

News/Features: Laser Points

New method for structuring brittle materials

Hard and brittle materials, like certain types of glass and sapphire, are difficult to process—even for lasers. Poor absorption at most wavelengths combined with poor heat-transfer properties make it difficult or impossible to realize structures in these materials.

Drilling microholes in plastic medical devices

High-speed injection molding and extruding are used extensively to manufacture disposable, plastic medical devices. These processes can produce a vast array of part shapes and configurations.

Cleaning up after laser processing

The cleanliness of laser-processed parts is of paramount importance, especially when producing medical, semiconductor and aerospace components.

Laser drilling really small holes

Laser-drilled holes with diameters less than 100µm usually are considered “small.” However, lasers can produce holes down to fractions of a micron across.

Patterning thin-film coatings with lasers

Thin-film-coating technology has played a huge role in the miniaturization of many products and devices. Among them are circuits, semiconductor wafers and MEMS devices, photovoltaic cells and optical devices—to name a few.

Lasers sometimes are used to apply thin-film coatings to surfaces. But the more common methods are chemical vapor deposition, physical vapor deposition and spray coating. All the processes uniformly coat the target surface.

Gas gives big assist to many lasing jobs

Many of today’s laser processes are performed with an assist gas, which is a pressurized stream of gas directed either coaxially with or lateral to the laser beam. In cases where an assist gas isn’t required, it’s often applied to reduce processing time and enhance workpiece quality.

Lasers contribute to next-gen microfluidic devices

Microfluidics is a multidisciplinary field encompassing physics, chemistry, engineering, flow dynamics and, frequently, biology. It deals with the manipulation and flow of liquids and gasses in miniature systems—typically submillimeter-sized. Microfluidic-device channels range in diameter from hundreds of nanometers to a couple hundred microns.

Basics of lasing high-aspect-ratio holes

When laser drilling holes in any material, the ratio of the hole’s depth to its diameter—the aspect ratio—must be taken into account. The reason has to do with the inevitability of taper on laser-cut materials. Usually taper is oriented such that the beam entry point is larger than the exit point (or bottom of a blind feature).

Taper limits how deep a laser-drilled hole can be. Further complicating matters is that ablated material can be deposited on the sides of holes, and at high repetition rates, ejected plasma and liquid interferes with the laser-drilling process.

The long and ultrashort of laser pulses

Every year, manufactured devices get smaller while boasting more capabilities. Traditional manufacturing techniques cannot address many of the process requirements related to producing these devices, such as denser and smaller features, and “clean” processing without subsequent cleaning steps. The pace also is accelerating in the laser-micromachining world, a result of the growing use of picosecond (ps) and femtosecond (fs) lasers.

Understanding and controlling taper when laser machining

Taper on the edges of laser-cut material is inevitable. Usually, this taper is oriented such that the laser beam entry point is larger than the exit point (or the bottom of “blind” features).

For the purposes of explaining taper—and due to the space constraints of this column—I’ll limit my discussion to laser-drilled holes.

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